#include <iostream>
#include <cstdint>
#include <vector>

using namespace std;

int main() {
	int n;
	vector<vector<int>> days;


	cin >> n;

	int start, end;
	for (int i = 0; i < n; i++) {
		cin >> start >> end;

		bool found_day = false;
		for (int j = 0; j < days.size(); j++) {
			vector<int>& day = days[j];

			if (end == day[0]) {
				day[0] = start;
				found_day = true;
				break;
			}
			else if (start == day[1]) {
				day[1] = end;
				found_day = true;
				break;
			}

		}

		if (!found_day) {
			days.push_back({start, end});
		}
	}

	cout << days.size();

	return 0;
}